Newbie lifting advice for a poor coward? ;)

Sue,
You know what happens when 50 year old women with back problems and some weight left to lose start and stay with an effective strength training program? They turn into very strong 51 or 52 year old women with far less or no back problems. If they diet just as effectively, they turn into lighter, stronger, 51 or 52 year old women. So can you. Its important that you got cleared first by your doctor - good job. (My wife, a new grandmother, is old enough to be your older sister, lifts astounding weights, is an advanced rock climber, and climbs 14,000 foot mountains on a monthly basis - and five or six years ago her training status and starting point was about the same as yours. My sister-in-law started training about four years ago, having never done anything more athletic than laps around a shopping mall, with the same amount of weight to lose as you. Today she is an advanced Crossfitter - not my thing, but she loves it - and looks like a model in a fitness magazine - at 50. Point is, as we used to say in my former line of work, "10,000 knuckleheads have done this, and so can you.")
You can strength train effectively regardless of your resource constraints and current status - all you need is you, and some basic knowledge. Maybe I can help (I am a certified strength coach, more importantly, an experienced one, with nothing to sell you, and have been doing this stuff for decades; wish I could help you in person, but this should get you off on the right track.)
To get started and start making progress, look at as many different YouTube videos as you can, from various bodyweight strength training sites, on the proper technique for four basic exercises, each of which can be done in an "easier" version as you start out, and progressively made into a more challenging version as you progress (and if you work at it, you will progress, probably much faster than you imagine).
The four "basics" I suggest to begin with are (1) squat, (2) pushup, (3) row, and (4) plank. At first, work toward becoming proficient at those four basic movements, and you can add additional movement patterns and exercises later. Those four movements strengthen the pushing muscles in your upper body (pushups), the pulling muscles in your upper body (rows), your legs (squats), and your torso (the so-called "core"), which are all of the many muscles that hold your pelvis, spine, shoulder blades, and collar bone together in a solid, safe, stable position, which is important for virtually everything we do.
It does not matter that you cannot do a regular pushup now - no worries. You can start with MUCH easier versions that change the angle to make them as easy as you like - for example, starting by just leaning against a wall and pushing away from it. When that gets easy, you simply make the angle a little steeper - for example, doing them facing a set of stairs, with your hands on the steps. Soon you'll be doing them on the floor (off your knees) and soon after that, the regular old way.
Its similar for squats - and don't worry about your ankles being tight - that's very common for many when they start. You can begin by just squatting a few inches or so, until your rear touches a chair, or a stack of books on a chair. You'll be able to go deeper as your strength improves. There are many great video resources on correct form for a basic bodyweight or "air" squat. (Bonus tip: to get your legs, hips, and back stronger for squatting or daily life, do this: walk up stairs, standing tall with good posture, without using the rail unless you need to stop, until that gets easier, then start walking up them two at a time - then three at a time - so simple, and so effective for the beginning trainer who may not use their legs much in daily life.)
Its similar for rows. I suggest ignoring that advice against doing one-arm rows - its ridiculous. You don't need a dumbbell, just something that weighs a few pounds to start with. A gallon milk jug full of water weighs eight pounds. You can hold one or two of them. Brace one hand on a chair to keep your back flat and parallel to the floor, and row that jug or jugs. As you get stronger - add water!
Planks - just like pushups - you just vary the angle a bit to get started - on your knees, on your elbows if needed, and with your elbows up on a chair or bench, if you need to - makes it easier.
With all this stuff, make sure you understand the form and what muscles you are supposed to be using. Its not that complicated - the most important things are (1) brace your midsection, from your shoulders to your hips, in a normal, tight, neutral position - your back should be held steady in the same position it would be if you were standing up with good posture, and (2) feel free to adjust the exact angle of your hands and feet to what feels solid and comfortable for you - again, those basics will be easy to understand if you watch several different videos of each exercise - its the stuff that everybody agrees on that actually matters.
When you start training, don't worry so much about the number of repetitions or sets of each exercise you do - think of it as "practice" and do as much as you enjoy. After you begin to get the hang of it, start with doing several repetitions of each basic exercise (which together are called a "set"), stopping and resting, then doing another set of several reps. At each level of difficulty - starting with the easiest version - work up to several sets of 8-10 reps. When you can do that, take the exercise up to a slightly more challenging version, and start working on that one.
Very important thing to realize about strength training is that its not something you do every single day - at least not the same movements day after day. You train, then take at least 48 hours to rest those muscles and let them get stronger, then exercise them again. You can pick two exercises and do them on Monday-Wed-Fri, and do two others on Tue-Thu-Sat.
Take a couple of weeks to "study up" on free videos - you do not need to pay money to strength train, or thanks to the internet, learn the basics. Look for the videos that talk about, and usually have in the title, the words "novice version," or "Progression" - those will tend to be the ones that show you the easiest versions that you should start with - for example, search YouTube for "Plank progression" or "planks for beginners novices" and you'll quickly find what you need to see.
I almost envy anyone who is just starting to train to get stronger - the progress you make if you work at it conscientiously over the first 6 months to a year is pretty amazing, and enormously fun and rewarding.
Best of luck to you!
Jim